1. Field of the Invention
The present invention relates generally to an apparatus of chemical mechanical polishing (CMP), and more particularly to, an improved apparatus of chemical mechanical polishing, which reduces air sharp pressure on the polish head for preventing the breakage of unpolished wafers.
2. Description of the Prior Art
Chemical mechanical polishing (CMP) is the only technology, which can provide a total planarization for ULSI process. This technology comes from IBM company and has been developed through many decades, and been already applied on many products, such as central processing unit (CPU). The philosophy is the planarization technique that uses a xe2x80x9cknife grinderxe2x80x9d like mechanical polishing method and in accompanies with a proper chemical reagent to planarize the rough sketch on wafer surface. Once all parameters are controlled well, chemical mechanical polishing can offer a smooth degree of more than 94%. Therefore, semiconductor manufacturers and the suppliers of facilities and chemicals all over the world are continually investing the development of CMP technology.
Referring to FIG. 1, which indicates a partial structural drawing the conventional traditional chemical mechanical polishing apparatus 10 which is composed of a wafer head 110, and a polish head 120. Wafer head 110 includes a wafer air inlet 112, a carrier firm 114 and a wear ring 116. Polish head 120 includes a polish air inlet 122, a polish air outlet 124, a pad air inlet 126 and a slurry diaphragm 128. When an unpolished wafer 118 is placed on the wafer head 110, the carrier firm 114 is put smoothly on the unpolished wafer 118, which is composed of high molecule polymerization, for example, plastic, rubber . . . etc, and then pouring in air from the wafer air inlet 112. The air pressure on the wafer head 110 is Pwafer, which is being pressed uniformly on the unpolished wafer 118 through the carrier firm 114, and the function of the wear ring 116 is to prevent the unpolished wafer 118 from slipping out from the wafer head 110 to break. Then, to pour air into the wafer air inlet 122 and the air will press uniformly on the slurry diaphragm 128, which is composed of high molecule polymerization, such as plastic, rubber . . . etc, and then leave from the polish air outlet 124. The air pressure on polish head 120 is Ppolish. Especially to take notice on the difference between Pwafer and Ppolish, which should be negative (it means xcex94P=Pwaferxe2x88x92Ppolish less than 0). By means of letting Ppolish to be greater than Pwafer unpolished wafer 118 can stick on the carrier firm 114 to process polishing. When the difference is positive (It means xcex94P=Pwaferxe2x88x92Ppolish greater than 0), the unpolished wafer 118 can""t stick on the carrier firm 114, and the unpolished wafer 118 will slip out the wear ring 116 and break. Besides, when polishing pad directly polishes the surface of the unpolished wafer 118, not only the slurry diaphragm 128 will release slurry to increase efficiently, but also the pad air inlet 126 will pour in air to maintain the system operation balance.
A partial air pressure regulation system is illustrated in FIG. 2. When air goes into the polish head 120 (through an air supply line 132), it needs to pass a regulator E/P first. Because the air pressure controlling system (not shown in Figure) must change way to send signal from digital to analog through this regulator and to adjust air pressure from the polish head 120. When the air leave the polish head 120 through another air line 134, it needs to pass a second polish pressure transducer P/I 138, which functions to change signal from analog to digital and to send back to air pressure control system. It owes to adjust air pressure through the wafer head 120.
But when pouring air to process chemical mechanical polishing, no matter the wafer air inlet 112, the polish air inlet 122 or the pad air inlet 126, the air pressure curves will all be the one illustrated in FIG. 3. The curve first show some time a sharp pressure, and gradually become air pressure steady state. In sharp pressure condition, due to the curve range of air pressure is huge:
(1) When Pwafer on the top point of the sharp pressure, and Ppolish is on the low point, it will increase the probability of xcex94P=Pwaferxe2x88x92Ppolish greater than 0, and the unpolished wafer 118 will slip out the wear ring 116 and break.
(2) When the pressure difference between Pwafer and Ppolish is too huge, it will cause slurry diaphragm 128 to break. In polishing process, slurry flows into the polish air inlet 122/outlet 124 from break and flows through the air supply line 132, 134 to the first regulator E/P 136, the second regulator E/P 138. It will make the real air pressure not be detected, and will send out a wrong signal to the air pressure control system. It will cause error on adjustment of air pressure, xcex94P=Pwaferxe2x88x92Ppolish greater than 0, and make unpolished wafer 118 slip out the wear ring 116 and break.
In accordance with the present invention, an improved chemical mechanical polishing apparatus is provided for processing chemical mechanical polishing that substantially overcomes drawbacks of above mentioned problems aroused form the conventional methods.
Accordingly, it is an object of the present invention to provide an improved chemical mechanical polishing apparatus which can reduce the sharp pressure and the probability of xcex94P=Pwaferxe2x88x92PPolish. greater than 0.
Another object of the present invention is to provide an improved chemical mechanical polishing apparatus that can detect whether slurry flows from the broken point of diaphragm to air supply line or not.
This invention is related to an improved chemical mechanical polishing apparatus, which is composed of a wafer head, a polish head, a damper and a sensor. The flowing speed of gas is reduced by making the diameter of the gas line connected to the damper air inlet smaller than the diameter of the gas line connected to the damper air outlet. The initial air sharp pressure is reduced and make xcex94P=Pwaferxe2x88x92Ppolish less than 0, by adding an air temporary storage machine in between the inlet and the outlet. It means that an unpolished wafer can stick on the carrier firm and won""t slip out to break when polishing. Besides, putting a sensor on the air lines under the air temporary storage machine, when slurry flows in the air line owing to the breaking of slurry diaphragm, the sensor will send a signal to a control system of the improved apparatus of chemical mechanical polishing, and make the related parts stop operating automatically to avoid breaking.